Columbia’s Greene Says You Have an Evil Doppelganger: Interview

The implications of current
mathematics lead to the radical notion that our universe is not
all there is: It’s just one among many.

“These ideas are speculative,” says Columbia University
physicist Brian Greene. “But if they’re right, this would be
the greatest upheaval ever to our understanding of reality.”

In his latest book, “The Hidden Reality: Parallel
Universes and the Deep Laws of the Cosmos,” Greene describes
the recent discoveries in physics and cosmology that point to
the existence of a multiverse.

We spoke in his spartan faculty office, decorated only with
mathematical equations.

The math we’re studying today, which emerges from
Einstein’s work, suggests our universe may not be the only
universe.

Lundborg: There are universes which in principle we’ll
never be able to access, but how do we find out about the other
ones?

The Multiverse

Greene: There are two good examples of multiverse proposals
where the other universes might interact with us in some way.

One is the idea that the big bang may not have been a
unique event. The math we’re studying to understand the origin
of our universe better suggests the event, the big bang, may
have occurred many times at various and far-flung places
throughout a much bigger cosmos. Each big bang gives rise to its
own expanding realm.

Lundborg: Presumably we can collide?

Greene: Yes, if we had a fender bender with another
universe there might be ripples created in the cosmic microwave
background radiation, the heat left over from the big bang.
Astronomers are looking at that heat right now to see if they
can find such ripples.

Lundborg: What’s the second path?

Greene: The other is a proposal that comes from string
theory, which can be tested at the Large Hadron Collider in
Geneva.

Protons are slammed against protons at extraordinarily high
velocity, and it’s possible according to the mathematics that
some of the debris created in those violent collisions could be
ejected off of our universe and migrate into other dimensions
that surround our universe.

Lundborg: We would see them disappear?

Greene: Exactly. The debris would take away energy -- we’d
have a missing energy signature that physicists are going to
look for.

The Doppelganger

Lundborg: Everyone can have an evil doppelganger -- how
does that work?

Greene: The argument for doppelgangers is pretty
straightforward. Assuming that space goes on infinitely far, in
any finite chunk, matter can only arrange itself in a finite
number of ways, like cards in a deck.

You and I are just a configuration of particles, so sooner
or later we’re going to repeat. Matter can almost repeat its
configuration but not repeat it identically.

Your physical body may repeat, but your mental
configuration can be a little bit different, so there might be
an evil version of you, and a version that loves skydiving.

Lundborg: So there’s a universe where Christ never was born
and another one where Hitler won the war?

Greene: Without a doubt, if these ideas are correct.

Lundborg: Is there a universe where the rules of math are
different?

Greene: Could be. That may be more of a philosophical
issue.

Lundborg: What’s your view of dark matter?

Greene: The most convincing candidates are supersymmetric
particles. These are particles like the ones that make us up --
electrons, quarks and so forth -- but heavier versions.

Lundborg: In your own scientific life, what was the most
exciting moment?

Greene: A result where we showed that unlike what Einstein
would have thought, space can tear apart and repair itself. The
technical term is topology changing transitions, but using the
math of string theory we went beyond Einstein and came to this
pretty startling conclusion.

Lundborg: What do you wish you could still discover?

Greene: I’d like to really understand where time comes
from. It’s so familiar and dictates so much of how we live and
what we do. Science still doesn’t have an answer to the
question: “What is time?”

Lundborg: The saddest thing in your book is that more and
more things will lie beyond our cosmic horizon.

Greene: The way we know space is expanding is we look out
through powerful telescopes and we see galaxies rushing away. If
the expansion is speeding up, those distant galaxies will go so
far we won’t be able to see them.

Looking out at deep space, we’ll see stillness, darkness,
blackness. That means our descendents a hundred billion years
from now won’t even know space is expanding -- their
observations may fool them.

Lundborg: Maybe our observations are fooling us?

Greene: It does raise questions about aspects of reality
that we hold dear.

Lundborg: Doesn’t your head hurt when you think about these
things?

Greene: Yes. In a good way.

(Zinta Lundborg is an editor for Muse, the arts and leisure
section of Bloomberg News. The opinions expressed are her own.
This interview was adapted from a longer conversation.)